620 Ingenieurwissenschaften und zugeordnete Tätigkeiten
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A numerical analysis of laser resonators with aberrations is presented. {T}he analysis shows that aberrations lead to large diffraction losses of laser resonators which are laid out to produce diffraction-limited beam quality. {S}tatic or dynamic compensation of the aberrations is possible and would yield much higher output power.
In der Mathematik ist es im Allgemeinen üblich, alle Fragen ohne die Berücksichtigung der Einheiten der verwendeten Größen zu behandeln. Wendet man dann die Gesetze und Ergebnisse auf Probleme der Physik und der Ingenieurwissenschaften an, so ergeben sich hinsichtlich der Einheitenanalyse für den kritischen Betrachter formal einige unbefriedigende Darstellungen. Da für den Physiker und den Ingenieur die Einheitenanalyse zu den besonders aussagekräftigen Kontrollmöglichkeiten zählt, muss dieser Bereich widerspruchsfrei und klar aufgebaut werden. Im folgenden wird der Versuch unternommen, die formalen Widersprüche anhand einiger einfacher Beispiele anschaulich herauszustellen; anschließend wird ein Vorschlag für eine konsistente Einheitenanalyse gemacht.
Adaptive laser resonators with deformable MOEMS mirrors under closed-loop control are discussed and experimental results are presented. The requirements for deformable mirrors and for closed-loop control systems of these mirrors are analyzed. Several deformable mirrors have been characterized and the results are presented. Currently available membrane mirrors deform under laser load and need further development before they can be used for aberration correction of solid state lasers above some tens of Watts. Nevertheless, the results are encouraging and the requirements are within reach of currently available technology. Finally, we demonstrate an Nd.YVO4-laser with a closed-loop adaptive resonator and more than 6 W of output power. The closed-loop system was able to compensate artificially introduced aberrations from a phase plate.
In order to avoid optical damage and non-linear effects, high-power, high-energy lasers of the petawatt class like PHELIX (petawatt high-energy laser for heavy-ion experiments) use large-aperture optics. Usually, chromatic aberration associated with these optical elements is neglected. By means of numerical simulations, we show how the chromatic aberration affects the focal intensity pattern. In particular, we make quantitative predictions of how chromatic aberration decreases the focused peak intensity. Furthermore, we prove the feasibility of a new interferometer that measures the temporal pulse front distortions which arise from expansion telescopes. We also propose a scheme that pre-compensates these distortions.